The present invention relates to a metal cylinder head gasket for an internal combustion engine, which is provided with an edge support shim to prevent deformation of a cylinder head.
An engine and a gasket installed therein for an automobile include cylinder bores, water holes, oil holes, bolt holes and so on. Since high pressure and temperature are formed in the cylinder bores when the engine is actuated, bolts for securing the engine parts together with the gasket are generally arranged around the cylinder bores to securely seal therearound. Other holes, such as water holes and oil holes, are situated near the cylinder bores, and are sealed by the tightening pressure of the bolts for sealing the cylinder bores.
Therefore, the other holes, i.e. water holes and oil holes, do not generally receive equal tightening pressure from the bolts. As a result, although the other holes have sealing means in the gasket, various sealing problems occur in these other holes.
On the other hand, in an engine where the cylinder bores are arranged linearly, since the sealing means are formed around the cylinder bores of the gasket, when the engine is assembled, the center area of the cylinder head is liable to bend upwardly while the longitudinal end areas are compressed close to the cylinder block. This causes an unbalanced tightening pressure to the sealing means for the cylinder bores and other holes, which may cause leakage of a fluid from the engine. Also, high tightening pressures are concentrated at the longitudinal end areas of the gasket.
In order to solve the problems, various attempts have been made. For example, in U.S. Pat. No. 5,427,389, beads are formed at longitudinal end portions of the gasket to support high tightening pressures applied thereto. Also, in U.S. Pat. No. 5,538,263, shims are located at the longitudinal end portions of the gasket to support the high tightening pressures. Further, in U.S. Pat. No. 5,439,234, beads around the cylinder bores located at the longitudinal end portions are doubled to support the strong tightening pressures applied thereto.
The support beads and the shims support the high tightening pressures applied to the longitudinal end areas of the engine to improve the unbalanced tightening pressures. However, since the tightening pressures applied to the longitudinal end portions may not be equal even in the longitudinal end portions, it is desirous to improve the supporting system for the tightening pressures at the longitudinal end portions.
The present invention has been made in view of the conventional gaskets, and an object of the invention is to provide a metal cylinder head gasket for an internal combustion engine, which can properly support the tightening pressures applied to the longitudinal end portions of the engine
Another object of the invention is to provide a metal cylinder head gasket as stated above, which allows sealing means for the cylinder bores and other holes to securely seal therearound.
A further object of the invention is to provide a metal cylinder head gasket as stated above, wherein the tightening pressures applied to the longitudinal end portions can be adjusted as desired.
Further objects and advantages of the invention will be apparent from the following description of the invention.